1. Field of the Invention
The present invention relates to a versatile matrix switching device which is effective for practical use of an automatic MDF in a communication network, and which can be widely used for a distribution frame for transmission lines.
2. Description of the Related Art
In a communication network, a main distribution frame (MDF) is disposed as a connecting device in a telephone office to connect a telephone set to exchange equipment. However, as shown in FIG. 1, the main distribution frame includes a terminal strip group 3 connected to a telephone set 1, a terminal strip group 4 connected to exchange equipment 2, and a jumper 5 for connecting the terminal strip groups 3 and 4, and has a matrix switching function for connecting an arbitrary telephone set 1 to the exchange equipment 2 via the jumper 5 in order to perform installation, transfer, and removal of the telephone set 1.
An example of this type of the prior art is disclosed in PCT No. 62-502642. FIG. 2 is a partially cutaway perspective view of a conventional pin board matrix. Referring to FIG. 2, reference numeral 101 denotes an upper board; 102, a lower board; 103 and 104, fixed boards; and 105, each linear spring of a metal wire disposed along an X-coordinate direction (to be referred to as an X-conductor linear spring). A plurality of X-conductor linear springs 105 are respectively supported by grooves 200 of the upper board 101 at equal intervals. For example, a telephone set is connected to an extending line of the X-conductor linear spring 105. Reference numeral 106 denotes each linear spring of a metal wire disposed along a Y-coordinate direction (to be referred to as a Y-conductor linear spring). The Y-conductor linear springs 106 perpendicularly intersect with the X-conductor linear springs 105. The plurality of Y-conductor linear springs 106 are respectively supported by grooves 201 of the lower board 102 at equal intervals. For example, exchange equipment is connected to an extending line of the Y-conductor linear spring 106. Reference numerals 107, 108, and 109 denote through holes, respectively. Each through hole 107 is formed in the fixed board 103, each through hole 108 is formed in the upper board 101, and each through hole 109 is formed in the lower board 102. These through holes respectively correspond to crossing points in a longitudinal direction of the X- and Y-conductors. Note that the X- and Y-conductor linear springs 105 and 106 partially cross the through holes of the corresponding boards in a matrix form. The boards are stacked and fixed to each other. Reference numeral 110 denotes a rigid conductor pin. When each conductor pin 110 is inserted into the though holes 107, 108, and 109, the corresponding X- and Y-conductor linear springs 105 and 106 are connected to each other through the conductor pin 110. With such an arrangement, when the conductor pin 110 is inserted into the through holes 107, 108, and 109, the X- and Y-conductor linear springs 105 and 106 are deformed to be in contact with the rigid conductor pin 110, and are electrically connected to each other. As a result, an inserting position of the conductor pin 110 is properly selected, so that a matrix switch for selectively connecting arbitrary X- and Y-conductors can be arranged.
Another example of the prior art is disclosed in U.S. Pat. No. 3,151,923. FIG. 3 is a sectional view of a main part of a pin board matrix. Referring to FIG. 3, reference numeral 111 denotes an upper board 1; 112, a lower board 1; 113, an insulating board; 114, an upper board 2; 115, a lower board 2; 116, an X.sub.1 -conductor linear spring; 117 and 117', Y.sub.1 -conductor linear springs; 118, an X.sub.2 -conductor linear spring; 119 and 119', Y.sub.2 -conductor linear springs; 120, a pin; 121, an insulator; 122 and 123, conductors; and 124, a through hole in each board. Other examples of the pin board matrix shown in FIG. 3 can be basically obtained by stacking two sets of matrix boards having the structures shown in FIG. 2 through the insulating board 113. The X.sub.1 -conductor linear spring 116 overlaps the Y.sub.1 -conductor linear springs 117 and 117' perpendicularly intersecting therewith, and the X.sub.2 -conductor linear spring 118 overlaps the Y.sub.2 -conductor linear springs 119 and 119' perpendicularly intersecting therewith. In the pin 120 for connecting an X.sub.1 conductor to a Y.sub.1 conductor, the conductors 122 and 123 are isolated from each other through the insulator 121 in correspondence with the X.sub.1 and Y.sub.1 conductors and the X.sub.2 and Y.sub.2 conductors in the matrix board.
With such an arrangement, when the connecting pin 120 is inserted into the through holes 124 of the boards, the X.sub.1 -conductor linear spring 116 electrically connected to the Y.sub.1 -conductor linear springs 117 and 117', and the X.sub.2 -conductor linear spring 118 is electrically connected to the Y.sub.2 -conductor linear springs 119 and 119'. More specifically, a matrix switch for connecting two portions of X- and Y-conductors upon one inserting operation of the pin can be arranged.
In the conventional pin board matrix shown in FIG. 2, however, in order to achieve a stable contact state, it is necessary to uniform the contact states between the conductor pin 110 and X- and Y-conductor linear springs 105 and 106. However, with this arrangement, it is necessary to form through holes in boards for supporting the springs in advance. More specifically, when the through holes are formed after the boards are stacked, the X- and Y-conductors are damaged. Therefore, when the boards which support the conductor springs are stacked, the through holes 107, 108, and 109 in the respective boards are necessarily misaligned, and contact states of the pin and metal conductor springs are not uniform upon insertion of the pin. This tendency typically occurs as pitches between adjacent metal springs are decreased, and it is difficult to achieve a decrease in pitch, i.e., a high-density arrangement.
In the above structure, since boards which support a large number of metal springs serving as conductors are carefully stacked and fixed to each other, it is unsuitable for mass production. The above-mentioned drawback also applies to the conventional pin board matrix shown in FIG. 3.